Jean Elcard, I'm playing RifE and have been getting frequent (about half the time I had 11 players on a huge map andnearly every time I had 15 players) CTDs during the AI's first turn. I saw speculation in the RifE bug thread that there was something about particular civs that might be causing it. However, I kept track of leaders in games with first turn CTDs and those without and finally had a game today with a CTD with leaders I had seen in games without, suggesting the issue was something else. On a whim, I unchecked flavourmod and have been CTD free the rest of the day, including one game with 30 players.
I don't know what the problem is but maybe some RifE civs are really picky about their starting positions and if their too far down the priority list, they get stuck somewhere the AI can't deal with. Which is more a RifE issue, but I see Valkrionn is like every third comment here, so this is still a good place to look into it.
I've been playing on large or huge pangaea maps with quite a few gameoptions on, All Unique Features, the two for extra orcs and animals, wild mana and mana guardians, I think are all the map related ones.